As a development of liquid crystal display tending to high pixels per inch (PPI), a technique of low temperature poly-silicon (LTPS) gradually replaces a technique of amorphous silicon.
The LTPS TFT array substrate generally employs an over coating flat layer, so the LTPS TFT array substrate does not like that the technique of amorphous silicon (without over coating) uses height differences among layers of an array substrate to form multiple photo spacers (PS) having the same height on a side of a color film substrate (CF) to form main PS and sub-PS structures. Therefore, LTPS usually needs a halftone technique to form the PSs with two different heights on the side of the CF to be used as the main PS and the sub-PS. If three PSs with different heights are required, a gray tone technique is employed to form the PSs with three different heights on the side of the CF to be used as the main PS, a first sub-PS and a second sub-PS.
Therefore, when the liquid crystal panel is made by the present technique, a complex fabricating art is required to form the PSs with different heights. In addition, using an expansive mask results a high fabricating cost, too.